1. Field of the Invention
The present invention relates to alumina, aluminum chelates and aluminoxanes, to methods of their making, and to products made thereof. In another aspect, the present invention relates to high surface area alumina, methods of making high surface area alumina, and to products made from high surface area alumina. In even another aspect, the present invention relates to methods of making high surface area alumina by Schiff base mediated hydrolysis. In still another aspect, the present invention relates to mesoporous alumina, to methods of making mesoporous alumina by Schiff base mediated hydrolysis, and to products made thereof. In yet another aspect, the present invention relates to a continuous process for making high surface area alumina. In even still another aspect, the present invention relates to a continuous process for making high surface area alumina by Schiff base mediated hydrolysis. In even yet another aspect, the present invention relates to a continuous process for making high surface area alumina by Schiff base mediated hydrolysis where the Schiff base product could be hydrolyzed to regenerate and allow recycle of the carbonyl compound and amine starting reagents. In still even another aspect, the present invention relates to varying the pore size of alumina. In still yet another aspect, the present invention relates to varying the pore size distribution of alumina. In yet even another aspect, the present invention relates to varying the mode of the pore distribution.
2. Description of the Related Art
Transition aluminas or activated aluminas are characterized by high specific surface areas making them useful for such applications as selective adsorbants, desiccants, and catalyst supports. The microstructure of alumina is strongly dependant upon synthesis conditions.
One of the problems related to the use of alumina as a catalyst support is deactivation by coke formation and pore plugging which hinders the diffusion of the reactants and products in and out of the catalyst particles. Large contribution of micropores to the specific surface area and wide pore size distribution both increase the deactivation rate. Conversely, high surface area aluminas with narrow pore size distributions that do not contain micropores lessen the deactivation rate. Therefore, synthesis of alumina with the proper pores size to reduce the deactivation rate that do not contain mircopores is of industrial interest.
The most common route to synthesize activated aluminas is via dehydration calcining of inorganic aluminum hydroxide gels obtained from the Bayer process. Aluminas may also be prepared by the hydrolysis and condensation of aluminum alkoxides. High surface area mesoporous alumina may additionally be obtained from an aluminum alkoxide with the aid of organic micelles.
The following are a sampling of the prior art related to making alumina.
U.S. Pat. No. 4,387,085 to Fanelli et al. discloses a process for preparing a high surface area alumina by heating a solution of alumina trialkoxide in a secondary or tertiary alcohol solvent to a sub-critical temperature at which the solvent decomposes to form water, and the water so formed hydrolyzes the aluminum trialkoxide. Solutions include aluminum tri-s-butoxide in s-butanol. The resultant aluminas have surface areas 500 m.sup.2 /g or greater.
U.S. Pat. No. 4,617,183 to Lewis et al. discloses a process for the vapor phase production of alumina by introducing steam into the vapor space above a heated, liquid phase aluminum alkoxide in which the aluminum alkoxide is hydrolyzed in a heated reaction zone down stream from the liquid alkoxide and collected as a dry powder without the necessity for utilizing conventional drying processes.
U.S. Pat. No. 4,744,974 to Lewis et al. discloses a process for producing alumina wherein an aluminum trialkyl is reacted with a substantially water immiscible alcohol to produce an aluminum alkoxide and an alkane, the reaction between the aluminum trialkyl and the alcohol being conducted in an organic phase, the alkoxide being hydrolyzed in an aqueous phase which is in contact with the organic phase, the alumina formed by hydrolysis of the aluminum alkoxide being recovered from the aqueous phase.
U.S. Pat. No. 5,055,019 to Meyer et al. discloses a process for the preparation of boehmitic alumina compounds having a purity of at least 99.95% Al.sub.2 O.sub.3. The compounds produced have a pore radii in the range of 3 to 100 nm. The preparation of such compounds is carried out by obtaining an alumina suspension from a neutral aluminum alkoxide hydrolysis, then aging the alumina suspension in an autoclave, preferably at a steam pressure of 1 to 30 barr which corresponds to at temperature of 100.degree. C. to 235.degree. C. for between 0.5 and 20 hours. The aging step of Meyer is preferably carried out with stirring at a peripheral speed of 1 to 6 m/s.
Fewer studies have been made using aluminum alkyl precursors. This is due to the extreme hydrolytic sensitivity of aluminum-carbon bonds. An example of a transition alumina prepared from aluminum alkyls is Catapal.RTM. produced by Vista Chemical Company. Catapal.RTM. is manufactured by the controlled oxidation of aluminum alkyls and hydrolysis of the resulting alkoxide in organic solvents using controlled amounts of water (Ziegler process). Catapal has high purity since refined aluminum metal is used as the aluminum source.
However, in spite of the prior art methods for producing alumina, they still suffer from one or more deficiencies as discussed above.
Thus there is a need in the art for new methods of making transition aluminas or activated aluminas.
There is another need in the art for making high surface are aluminas.
There is even another need in the art for making high surface area mesoporous alumina.